It has now recalled all listening devices until its animal management officers have received refresher training to ensure they followed correct procedure.

The council has 18 devices and has used them for the last five years.

JOHN KIRK-ANDERSON/FAIRFAX NZ

The box Jenny Bennett found in her garden, planted without her knowledge by the city council, contained a recording device.

Jenny Bennett found the device under a shrub on her Avonside property last week.

"I thought it was a piece of rubbish and went to pick it up," she said.

What she found was a beige box with "Dog Control" written on it and a phone number for the head of the council's animal management team.

Bennett opened up the box and found a recording device with a microphone inside.

"I'm pretty shocked. We just didn't think they could do that."

She said she would have consented to it being there if the council had asked them.

The Bennetts, who have responsible dog owner status with the council, received a complaint about their four-year-old schnauzer, Arthur, barking about eight months ago. They said they had done everything dog control asked of them to prevent him barking.

They got him a mate to play with, Jeb, a six-month-old bitzer, and that seemed to work for a while, but about three weeks ago they received another visit from dog control. On the advice of the dog control officer they installed a gate, so the dogs could not see people walking by.

Dog control visited again last week and the officer did not mention the device, but when she left the property Tim Bennett saw her go to the shrub and look for it. When she could not find it, she left the property without talking to him again.

Human rights lawyer Michael Bott said the council's action's were "outrageous" and breached the couple's right to privacy.

"It's the sort of thing you would expect by someone from the KGB or more lately the GCSB (Government Communications Security Bureau)."

He said the council's actions seemed "excessive, disproportionate and on the face of it unlawful".

"The dogs might be barking but in another sense the council seems to be barking itself."

He did not know of any statutory power the council would have to covertly placesurveillance equipment on someone's property.

Council regulatory compliance head Tracey Weston said the listening devices were used once all other steps had been taken to determine excessive dog barking.

She said the device on the Bennett's property was the only one placed without permission.

"The council's practice is to only use these listening devices on a property with the permission of the owner."

The device was able to pick up voices, but animal management officers could not recall a situation where they had heard conversations on a recording. The council's policy was to disregard anything heard on the recording other than barking, Weston said.

The council received 6282 complaints about barking dogs, fouling and bylaw breaches in the 2014/15 year, up from 5772 the previous year.